Cementing plug



Jan. 14, 1941. R s. KA". 2,228,630

CEMENTING PLUG Filed July 2, 1940 RAY .Si KAI/Q,

mgm/amm Patented Jan. 14, l

UNITED STATES cEMENmG PLUG Bay S. Kail, Houston, Tex., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation oi' California Application July 2, 1940, Serial No. 343,591

1l Claims.

This invention relates to devices employed in the cementing oi' wells, being particularly directed to that type of cementing plug which is capable of forcing a preceding charge of cement down through a well casing. j

In the plug method of cementing wells, a charge of cement -is pumped down the casing between upper and lower plugs to prevent co-mingling of the cement with the preceding or following columns of mud or iluid, insuring the` ejection of an uncontaminated batch of cement slurry from the casing. It is usual practice to displace the cement through a casing shoe or collar having a back pressure device, to prevent return ilow of the cement slurry into the casing after the pressure through a casing shoe or collar lacking back pres-v sure devices may iiow reversely into the casing upon release of the pump pressure.

Accordingly, it is an object of the present invention to provide a cementing plug capable of forcing a preceding charge of cement slurry down through a casing string, the plug becoming anchored to the casing against movement in an upward direction to prevent reverse ow of the cement into the casing.

It is a further object of the invention to provide a cementing plug hydraulically movable down through a casing to eject a preceding charge of cement slurry therefrom', the plug being so constructed as to be anchored in packed-Cif condition in the casing to prevent return flow of the cement into the casing.

This invention has other objects that will becoming apparent from a consideration of the embodiment shown in the drawing accompanying casing, disclosing the cementing plug with its parts in retracted position; and

Figure 2 is a view similar to Figure 1, illustrating the cementing plug set in packed-oil' condition within the casing.

The cementing plug A consists of a body I0, which can be of generally tubular form, having a body guide I I threaded on its lower end to close its axial bore. An annular packing I2 of rubber or similar material isdisposed around the exterior of the body, being suitably coupled to the guide I I at one end and to a frusta-conical expander I3 at its other end. In the specic example disclosed, such couplingA is eifected by the interlocking anges I4, I5, I6 on the packing, guide, and ex- 10 segmental slips II is disposed circumferentially 15 around the body, with their inner surfaces adapted to slide along the companion expander surface I3a radially into engagement with the wall of the casing B. Initially, these slips are held in retracted position by shear screws I8 securing them 20 to the body, and by a second set of shear screws I9 securing them to the frusto-conical expander I3. The second set of shear screws I9 preferably has a greater shear value than the first-mentioned set I3, for the reasons hereinafter advanced.

A swab cup of rubber or any other suitable packing material is disposed around the upper portion of the plug body with its lower end suitably secured to a retainer ring 2|, as by means of the respective interlocking anges 22, 23 provided on the ring and base of the swab cup. 'Ihe swab cup 20 and retainer ring 2l can slide along the surface of the body, but they are initially held in an upper position with the ring contacting or spaced from the upper ends of the slips I1 by one or more shear screws 24 passing ,through the ring and threaded into the body. As a precautionary measure, a stop ring 25 is threaded on the upper end of the body to prevent inadvertent removal of the swab cup and retainer ring after the parts have been assembled.

'I'he cementing plug A, with its parts in retracted position (see Figure 1), is disposed on top of a charge of cement slurry, the upwardly directed lip 20a of the swab cup having slidable, sealing engagement with the wall of the casing B. The application of pressure to the fluid above the plug will expand the swab cup into engagement with the casing over a greater area and will force the plug together with the preceding cement slurry downwardly in the casing, causing the cement t0 be ejected through a guide shoe (not shown) or through a baille collar C forming part of the string of casing. 'Ihis collar is provided `with a cement strikes the baille 28,' assurance is had that the desired quantity of cement slurry has been elected from the casing. Subsequent increase in the pressureoi' the fluid on top o! Athe cementing plug will produce a shearing oi the screws 24 holding the retainer ring 2l to the body Il and allow the `swab cup 20 to move downwardly along the body, its cooperable retainer ring engsin the slipsJ'l `to enable further application loi hydraulic presv sure on the swab cup to'shear the upper set ci screws I8. Continued imposition of pressure on the swab cup will force the slips I'I and cone Il as a `unit down along the body to compress the,

packing I2 and form an annular seal between the body and the wall ot the casing, preventing the passage ot'iiuid therebetween in either direction. Increase oi the iiuid pressure on the plug will cause the swab cup 2l and its retainer ring 2| to disrupt the screws Is of greatershear value securing the slips to the cone expander, and force the slips i1 along the taperedsurface i3d of the cone into engagement with the casing.

It will be noted that the slips are provided with upwardly facing wickets Ila so as to'anchor the plug to the casing against' displacement in an upward direction. Ii' the cement slurry tends to ilow back into thecasing, or if any other pressure from below is exerted on the plug. the wedging action of the cone expander Il in the slips will be enhanced, anchoring the `wickers i'la more rmly in the wall of the casing. This same force acting on the bottom of the plug will also serve to compress the annular packing I2 more iirmly between the body and casing. Similarly, increase in the pressure on top of the plug. or its continued application, will tend to force the slips downwardly and increase the wedging action of the cone. A

It is, therefore, apparent that a cement plug has been provided which is particularly useful in tions of the casing string lacking of the fluid into the casing. The plug described takes the place of the usual back pressure valve,v

serving to accomplish the same purposes in a positive manner because of its anchoring to the casing through the agency of the slips Il and the rgzlazannular seal provided by the packing mem- Although specically designed 'for use'in casing strings devoid of back pressure valves, it is to be understood thatthe cementing plug is also capable of use with float shoes, float collars, and the like, offering further assurance thatthe cement cannot pass back into the casing should the back pressure valves leak. The various parts of the plus Aare preferably made of some readily drillable materiaLsuch as cast iron or an aluminum alloy, to permit its .removal by a suitable drilling tool, along with the drillable plug 26,. should a free passage through the casing string be required.

I claim:

l. A cementing plug adaptedto be moved down a well casing, including a body, normally retraced means carried by said `body for engagement with such casing, and hydraulically actuated means for shifting said normally retracted means into engagement with said casing, said hydraulically actuated means being adapted for slidable assenso seaungwnmtwlmmdcasinaassaxdpmg moves downwardly therewithin.

-aseemenung plus adspdmbepumped' down a well casing, including a body, normally retracted means carried by said body for 'engagement with such casing, and annular hydraulically `for-shiiting said expander andslips with respect to one another to move thelatter into contact with said casing, said annular means being20 adapted for slidable sealing contact with said casingassaid plug moves downwardly therewithin.

4. A cementing plug adapted to .be pumped down awell casing, including a body, an expander on said body, slips cooperable with said expander for engagement with said casing, and

a swab movable along said body for shifting said slips along said expander into contact with said casing.

' 5. A cementing plug adapted to be moved down a well casing, including a body; an expander. on

said body, slips cooperable with said expander for -dowri a well casing, including a body, an expander on said body, slips cooperable with said expander for anchoring said body to said casing, annular packing on said body, and a swab slidable along said body for moving said slips and annular packing into engagement with said casing.

7. A cementing plug adapted for movement down a well casing, including a body, an expander on said body, normally retracted slips cooperable with said expander for anchoring said body to said casing against upward movement, annular packing on said body, and a swab having an upwardly directed casing engaging lip slidable down along said body for moving said slips and annular packdown a well casing, including a body, a conical 1 rected casing engaging lip slidable down along said body to disrupt said irangible means and move said slips and annular packing member into engagement with said casing.

10. A cementing plug adapted for movement" down a well casing, including a tubular body, a conical expander slidable on said body. slips cooperable with said expander for anchoring said body to said' casing against upward movement, frangible means for securing said slips to 'said body and expander, a guide secured to the bottom of said body for closing the same, an annular packing member having its ends fixed, respectively, to said guide and expander, and a swab having an upwardly directed casing engaging lip slidable down along said body to disrupt said frangible means and move said slips into engagement with said casing, such movement of said swab sliding said expander down along said body for compressing said annular packing member between said body and casing.

11. A cementing plug as dened in claim 10, said frangible means comprising separate sets of shear pins initially holding said slips to said body and expander, said expander pins having a greater shear value than said body pins.

RAY S. KAIL. 

